1. Field of the Invention
The present invention relates to an absorbent for separating acidic gases from a gas mixture, and more particularly, to a carbon dioxide separating absorbents having a high reaction rate with carbon dioxide, high absorption ability, and less energy consumption for regenerating the absorbents.
2. Description of the Related Art
Absorption, distillation, adsorption, membrane separation, and the like are contemporary applicable techniques for separating carbon dioxide from exhaust gas and factory flue gas. Absorption and distillation techniques among them are applicable to an exhaust gas source such that the concentration of a subject component is equal to or higher than 10% and a large quantity of flue gas is emitted, while adsorption and membrane separation techniques are applicable to an exhaust gas source such that the concentration of a subject component is low and a small quantity of flue gas is emitted.
Carbon dioxide separation process by absorption is a technique of selective separation of carbon dioxide by which flue gas containing carbon dioxide is brought into contact with various kinds of absorbents. This technique is classified into physisorption and chemisorption according to the characteristics of the absorbents. Specifically, absorption and separation techniques by using an alkanolamine absorbent solution has been widely used in chemical industries to eliminate acidic gases such as CO2, H2S, and COS.
Monoethanolamine (MEA) and diethanol amine (DEA) have been widely used because of high reaction rate, however, they have disadvantages such as high corrosiveness and heat deterioration. Further, N-methyl diethanolamine (MDEA) has low corrosiveness and regenerated heat and a low absorption rate.
Recently, studies about sterically hindered amines as a series of new alkanolamine absorbents are actively in progress. These sterically hindered amines have advantages of absorption capacity, selectivity of an acidic gas, and requiring less energy for regeneration but those alkanolamies have a disadvantage of low absorption rate.
Korean Unexamined Patent Application Publication No. 2005-0007477 discloses potassium taurate as an absorbent, however after the reaction with carbon dioxide precipitates to be removed are produced. Further, since potassium taurate has a lower carbon dioxide absorption rate than existing absorbents and is a less sterically hindered primary ammonium salt, more energy is required to separate carbon dioxide.
Japanese Patent No. 2,871,335 disclosed that a piperazine derivative is used as an accelerator for a secondary amine such as 2-amino-2-methyl-1-propanol (AMP) or (2-aminoethyl)ethanol which is a bulky amine bonded to a tertiary carbon.